Here is the problem:
In cue 2 I fade a channel from full to 50% in 4 seconds
In cue 3 I fade the same channel to 0% in 50 seconds.
No when I press [GO] halfway through the fading of cue 2, the look on stage is wrong for almost the whole 50 seconds. It's fading in 50 seconds not from 50% but from 75%.

I would like to see the console first finish the whole fade for the channels that have conflicting levels or fade the level in the time of the first cue until it has reached the level it should have had on the moment in the fade of the second cue.

What I am asking for is something else: I would like the first fade to be completely finished for those particularly channels that are changing in both cues. I think that should happen in the time of the cue that was first triggered. This way you avoid a jump and you are a bit closer to what was intended by the designer.

In case the second cue fades slower then the first cue, it should fade in the faster time I guess.

My goal is to stay closer to the original intention of the cue and still be able to press go faster then foreseen.

What Bobby describes is the horrible behavior of many a preset console - Press GO before a cue completes and we snap to the end of the first cue so we can execute the second. Yuck. Still less confusing than the console(name of which long ago lost) which had a GO/STOP and a BACK instead of a GO and STOP/BACK - that really prevented "jumping" the GO.

So you are saying with the GO on cue 3, the channel should continue on to 50% at the rate of 12.5% per second and then fade from 50% to zero finishing at 50 seconds after the GO on cue 3. Yikes. I can see a certain logic there but it seem very hard to manage.

If this happened frequently enough in the run of the show I'd consider splitting cue 3 into Cue 3 Part A, Cue 3 Part B and Cue 3.5. I'd use 3A(50 seconds) for the non-overlapping channels, 3B(2 seconds) for the overlapping channels with a fast time to complete the fade to 50% and 3.5(48 seconds) for the overlapping channels to slowly fade out.